Electronic squib firing sequencer

ABSTRACT

In a projectile carrying a plurality of payloads which are to be sequentially ejected, an electronic circuit for selectively firing ejection charges, which comprises a series of interlocked switches that are held in one position by the presence of the projectile backplate. Upon release of the backplate the switches assume a second position and thereby permit the application of voltage to an R-C network in which the capacitors charge up to a voltage sufficient to overcome a zener diode that in turn activates a silicon controlled rectifier via its conrol electrode. The rectifier is connected in series with an electrical energy source, ground interlock switches and a squib so as to fire the same sequentially after some selected period set by each of the R-C networks. The ground interlocks being connected so as to effectively short circuit the squibs prior to release of the backplate.

United States Patent 11 1 Derk 1451 Sept. 11, 1973 ELECTRONIC SQUIBFIRING SEQUENCER [75] Inventor: Joseph T. Derk, Wharton, NJ.

[73] Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

[22] Filed: Apr. 5, 1971 [21] Appl. No.: 131,206

[52] U.S. Cl. l02/70.2 R, 102/82 [51] Int. Cl. F421) 22/30, F42c 9/00[58] Field of Search 102/70.2 R, 82, 70 R, 102/28 P; 181/.5 FS

[56] References Cited UNITED STATES PATENTS 3,513,355 5/1970 Shanksl02/70.2 R 3,618,525 1/1969 Fritz l02/70.2 R

Primary Examiner-Benjamin A. Borchelt Assistant Examiner-J. V, DoramusAtt0rneyl-larry M. Saragovitz, Edward J. Kelly and Herbert Berl [57]ABSTRACT In a projectile carrying a plurality of payloads which are tobe sequentially ejected, an electronic circuit for selectively firingejection charges, which comprises a series of interlocked switches thatare held in one position by the presence of the projectile backplate.Upon release of the backplate the switches assume a second position andthereby permit the application of voltage to an R-C network in which thecapacitors charge up to a voltage sufficient to overcome a zener diodethat in turn activates a silicon controlled rectifier via its conrolelectrode. The rectifier is connected in series with an electricalenergy source, ground interlock switches and a squib so as to fire thesame sequentially after some selected period set by each of the R-Cnetworks. The ground interlocks being connected so as to effectivelyshort circuit the squibs prior to release of the backplate.

7 Claims, 2 Drawing Figures Patented Sept. 11, 1973' 2 Sheets-Sheet lFIG.I

INVENTOR) JOSEPH T. DERK ELECTRONIC SQUIB FIRING SEQUENCER The inventiondescribed herein may be manufactured, used and licensed by or for theGovernment for governmental purposes without the payment to me of anyroyalty thereon.

BACKGROUND OF THE INVENTION The present invention relates to system forejecting a plurality of payloads from a projectile and more particularlypertains to an electronic circuit for sequentially initiating thepayload release at selected intervals and incorporates thereinmalfunction, safety interlocks.

In the field of sequential payload ejection, it has been the generalpractice to employ some pyrotechnic delay composition whose initiationwas dependent of the activation of an explosive used to blow off thebackplate. This method has proved unsatisfactory in that the ejectiontimes were unpredictable and without proper function times, pluralpayloads would be simultaneously ejected resulting in an action whichdefeated the primary delivery purpose. In addition, where the payloadswere deployed with parachutes, fouling thereof occurs in many instances.This problem has been satisfactorily overcome by the present invention.

SUMMARY OF THE INVENTION The general purpose of this invention is toprovide a sequential squib firing circuit for payload ejection that hasall the advantages of similarly employed prior art devices and has noneof the above described disadvantages. To attain this, the presentinvention provides, for each payload, a unique circuit arrangementinterlocked with the backplate and which includes an R-C network coupledto overcome a Zener diode and whose charging commences upon the releaseof said plate. The diode is connected to turn on a silicon controlledrectifier which in turn permits the squib to be tired from an electricalsource. Each R-C network includes selected components to allowindependent setting of the time period between plate release and payloadejection.

An object of the presentinvention is to provide a simple, reliable, safeand inexpensive squib firing sequencer circuit for initiating theejection of payloads from a projectile at selected intervals.

Another object is the provision of an electronic circuit forsequentially firing a plurality of squibs which, circuit is capable ofwithstanding setback forces of 30 s Other objects and many of theattendant advantages of this invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view,partially in section, of a missile in which the subject invention isemployed; and,

FIG. 2 is a schematic of an embodiment made in accordance with theprinciple of this invention.

DESCRIPTION OF A PREFERRED EMBODIMENT The missile of FIG. 1 carries atits nose end a pair of dual thrust rocket motors 11 while the remainingportion of the missile is provided with a payload chamber 12 thatcontains the ejection control system 13 as well as three payloads 14(two of which are shown).

The rear end of the missile is closed by a backplate 15 that is held inposition by four radial release pins 16 whose central area carries apiston arrangement 17 communicating with a forward black powder charge18 through blast tube 19. Each payload is housed in a launch tube 20 andat the forward end thereof includes an ejection piston 21 that isactivated by an ejection charge 22 in which is disposed a squib 23, sothat when the squib is activated it will fire the charge and theexpanding gases will displace the piston rearwardly against the nose ofthe payload, driving or ejecting the payload after the backplate hasbeen released. The sequence for removal of the backplate is as follows:A mechanical time fuze 24 is activated at a prescribed time afterlaunch, based on the desired range and it initiates an explosive trainin the charge 18 generating a pressure wave which travels down the blasttube 19 and acts against the backplate piston arrangement 17 to blow offthe backplate. The three small payload charges 22 are sequential ignitedby the subject embodiment of this invention, namely, the electronicsquib firing sequencer or ejection control system 13 and each one inturn acts on the payload ejection piston to launch the payloads. Thesepayloads are provided with attached drogue parachutes 25 which aredeployed as soon as the load clears the missile and serve to limit theimpact velocity of the payload. v

Having described the general environment and operation of the mainelements, attention is now directed toward the subject inventiveembodiment which comprises two separate physical structures but a singleelectrical system. A plurality of micro switches in a support 26 arepositioned against the backplate so that they will assume their unbiasedswitch position when the plate against which they abut is removed. Theremaining portion of the electronics is disposed forward of the payloadwith the squibs adjacent the ejection charges. The seven bias or microswitches 27-33, as shown in FIG. 2, with their movable arms 34-40 (forthe dotted position) in the biased position as when in abutting relationto the backplate and for the solid showing with the backplate removed.Two switches are provided for each squib, with the main power switch 30having its arm 37 connected through a single-pole single throw 41 switchto a battery 42 and its fixed contact connected to the anode resistor43-45 of an asymmetrical conducting means such as silicon controlledrectifiers (SCR) 46-48. With switch 30 open, no power is present at theSCR anodes 46-48 so that no. current can flow from the anode to thecathode 52-54 even if the gate electrode 55-57 were accidentallyenergized. One

stationary contact 59-64 of each control switch is connected to theground or the negative side of the source or battery 42 as well as tonegative side of batteries 65-67. The other stationary contacts 68-70 ofR-C gate switches 27-29 areconnected via resistors 71-73 to the high orpositive terminals of batteries 65-67. The movable arms 34-36 of thegate switch are connected to charging capacitors 74-76 so that when thearm is released (backplate removed) it effectively places the batteryacross the delay means or R-C network (71-74, 72-75, 73-76) andcommences charging of the capacitor. At the same time the movable arms38-40 of squib switches 31-33 open from their fixed contacts and therebyremove ground from the squibs 23, 23a, 23b and power switch 30 connectsthe positive terminal of battery 42 to anode resistors 43-45 and groundvia capacitors 77-79. Charging capacitors 74-76 commence to chargetoward the battery voltage at a rate dependent on their time constantsor the values of resistance and capacitance. When the potential on eachcapacitor reaches the breakdown or conduction voltage of the Zener diode80-82 it then conducts (discharges capacitor), via discharge dividerresistors 83-85, 86-88 providing a voltage at their junction and on theSCR gates 55-58. This voltage is sufficient to turn the SCR on andconduction takes place between the anode and cathode through the squib23 to the battery 42 negative. This passage of current through the squibfires it almost instantaneously. By properly adjusting the R-C timeconstant ofeach squib circuit, they can be made to fire sequentiallywith variable time differentials. The timing adjustment can most readilybe accomplished by setting variable resistors 71-73 to the selectedvalues.

The system operation can best be summarized as follows: The missile fuzetimer fires a powder charge which blows off the backplate cover andreleases the seven micro switches mounted on the rear of the missile.The switches are activated as the backplate is blown clear of themissile. Three of the switches serve to short out the squibs with thebackplate in place while another three are utilized to activate the R-Ctime voltages across the capacitors when the backplate is blown off. Theremaining switch maintains an open circuit for the firing voltage at theSCR anode and closes the circuit only upon release of the backplate.When one of the capacitors charges up sufficiently, the Zener diodeconducts and the first SCR conducts from its anode to cathode and firesthe first squib. The time interval is dependent on the R-C time constantand by appropriately selecting the resistance for each circuit, thesquibs will be fired sequentially.

It should be understood, of course, that the foregoing disclosurerelates only to a preferred embodiment of the invention and thatnumerous modifications or alterations may be made therein withoutdeparting from the spirit and the scope of the invention as set forth inthe appended claims.

I claim:

1. A missile electronic firing system for sequentially activating aplurality of squibs for sequential ejections of payloads from themissile, which missile is provided with a mechanism for releasing thebackplate thereof at some time after launch, said firing system comprisaplurality of squib firing circuits, one for each squib,

and each circuit having included therein,

an asymmetrical electrical conducting means having a control elementwhereby when a specific voltage is applied thereto said conducting meanswill conduct between its input and output.

a source of electrical energy having a positive and a ground terminal,

an independently variable time delay means connected to said controlelement,

a first bias switch connected intermediate said source and said delaymeans and disposed in abutting relation to said backplate and activatedby the release thereof to apply said source to said delay means,

a pair of terminals, one of said terminals connected to the output ofsaid conducting means and the other terminal connected to said groundterminal of said source,

a main source of electrical energy connected across the input of each ofsaid conducting means and said ground terminal of said source,

whereby when a squib is connected across each of said pairs of terminalsthe squibs will be activated at different times after said backplate isreleased which will cause said payloads to be ejected sequentially.

2. The system according to claim 1 wherein said delay means includes aseries R-C connected resistor and capacitor and a Zener diode and asecond resistor.

3. The system according to claim 2 wherein said conducting means is asilicon controlled rectifier.

4. The system according to claim 3 wherein said first bias switchincludes a pair of stationary contacts and a movable pole biased tocontact one of said contacts and physically deflectable to contact theother of said stationary contacts when in abutting relation to saidbackplate, said one contact connected to said ground terminal of saidsource and said other contact connected to said positive terminal ofsaid source, said pole connected to said R-C junction.

5. The system according to claim 4 further including for each firingcircuit a single pole-single throw bias switch in abutting relation tosaid backplate for connecting said ground terminal to said output ofsaid silicon rectifier and removing the same when said backplate isreleased.

6. The system according to claim 5 further including another singlepole-single throw bias switch connected intermediate said main sourceand the anode input of said silicon rectifier.

7. The system according to claim 6 wherein all of said bias switches aremicroswitches.

1. A missile electronic firing system for sequentially activating aplurality of squibs for sequential ejections of payloads from themissile, which missile is provided with a mechanism for releasing thebackplate thereof at some time after launch, said firing systemcomprising: a plurality of squib firing circuits, one for each squib,and each circuit having included therein, an asymmetrical electricalconducting means having a control element whereby when a specificvoltage is applied thereto said conducting means will conduct betweenits input and output. a source of electrical energy having a positiveand a ground terminal, an independently variable time delay meansconnected to said control element, a first bias switch connectedintermediate said source and said delay means and disposed in abuttingrelation to said backplate and activated by the release thereof to applysaid source to said delay means, a pair of terminals, one of saidterminals connected to the output of said conducting means and the otherterminal connected to said ground terminal of said source, a main sourceof electrical energy connected across the input of each of saidconducting means and said ground terminal of said source, whereby when asquib is connected across each of said pairs of terminals the squibswill be activated at different times after said backplate is releasedwhich will cause said payloads to be ejected sequentially.
 2. The systemaccording to claim 1 wherein said delay means includes a series R-Cconnected resisTor and capacitor and a Zener diode and a secondresistor.
 3. The system according to claim 2 wherein said conductingmeans is a silicon controlled rectifier.
 4. The system according toclaim 3 wherein said first bias switch includes a pair of stationarycontacts and a movable pole biased to contact one of said contacts andphysically deflectable to contact the other of said stationary contactswhen in abutting relation to said backplate, said one contact connectedto said ground terminal of said source and said other contact connectedto said positive terminal of said source, said pole connected to saidR-C junction.
 5. The system according to claim 4 further including foreach firing circuit a single pole-single throw bias switch in abuttingrelation to said backplate for connecting said ground terminal to saidoutput of said silicon rectifier and removing the same when saidbackplate is released.
 6. The system according to claim 5 furtherincluding another single pole-single throw bias switch connectedintermediate said main source and the anode input of said siliconrectifier.
 7. The system according to claim 6 wherein all of said biasswitches are microswitches.